/****************************************************************************
 * net/tcp/tcp_backlog.c
 *
 *   Copyright (C) 2008-2009, 2011-2013, 2020 Gregory Nutt. All rights
 *     reserved.
 *   Author: Gregory Nutt <gnutt@nuttx.org>
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 * 3. Neither the name NuttX nor the names of its contributors may be
 *    used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 *
 ****************************************************************************/

/****************************************************************************
 * Included Files
 ****************************************************************************/

#include <nuttx/net/netconfig.h>
#if defined(CONFIG_NET) && defined(CONFIG_NET_TCP) && defined(CONFIG_NET_TCPBACKLOG)

#include <stdint.h>
#include <stdbool.h>
#include <stdlib.h>
#include <queue.h>
#include <debug.h>

#include <nuttx/kmalloc.h>
#include <nuttx/net/net.h>

#include "devif/devif.h"
#include "tcp/tcp.h"

/****************************************************************************
 * Public Functions
 ****************************************************************************/

/****************************************************************************
 * Name: tcp_backlogcreate
 *
 * Description:
 *   Called from the listen() logic to setup the backlog as specified in the
 *   the listen arguments.
 *
 * Assumptions:
 *   Called from normal task logic.  The network may or may not be locked.
 *
 ****************************************************************************/

int tcp_backlogcreate(FAR struct tcp_conn_s *conn, int nblg)
{
  FAR struct tcp_backlog_s     *bls = NULL;
  FAR struct tcp_blcontainer_s *blc;
  int size;
  int offset;
  int i;

  ninfo("conn=%p nblg=%d\n", conn, nblg);

#ifdef CONFIG_DEBUG_FEATURES
  if (!conn)
    {
      return -EINVAL;
    }
#endif

  /* Then allocate the backlog as requested */

  if (nblg > 0)
    {
      /* nblog value must less than SOMAXCONN */

      if (nblg > SOMAXCONN)
        {
          nblg = SOMAXCONN;
        }

      /* Align the list of backlog structures to 32-bit boundaries.  This
       * may be excessive on 24-16-bit address machines; and insufficient
       * on 64-bit address machines -- REVISIT
       */

      offset = (sizeof(struct tcp_backlog_s) + 3) & ~3;

      /* Then determine the full size of the allocation include the
       * tcp_backlog_s, a pre-allocated array of struct tcp_blcontainer_s
       * and alignment padding
       */

      size = offset + nblg * sizeof(struct tcp_blcontainer_s);

      /* Then allocate that much */

      bls = (FAR struct tcp_backlog_s *)kmm_zalloc(size);
      if (!bls)
        {
          nerr("ERROR: Failed to allocate backlog\n");
          return -ENOMEM;
        }

      /* Then add all of the pre-allocated containers to the free list */

      blc = (FAR struct tcp_blcontainer_s *)(((FAR uint8_t *)bls) + offset);
      for (i = 0; i < nblg; i++)
        {
          sq_addfirst(&blc->bc_node, &bls->bl_free);
          blc++;
        }
    }

  /* Destroy any existing backlog (shouldn't be any) */

  net_lock();
  tcp_backlogdestroy(conn);

  /* Now install the backlog tear-off in the connection.  NOTE that bls may
   * actually be NULL if nblg is <= 0;  In that case, we are disabling backlog
   * support.  Since the network is locked, destroying the old backlog and
   * replace it with the new is an atomic operation
   */

  conn->backlog = bls;
  net_unlock();
  return OK;
}

/****************************************************************************
 * Name: tcp_backlogdestroy
 *
 * Description:
 *   (1) Called from tcp_free() whenever a connection is freed.
 *   (2) Called from tcp_backlogcreate() to destroy any old backlog
 *
 *   NOTE: This function may re-enter tcp_free when a connection that
 *   is freed that has pending connections.
 *
 * Assumptions:
 *   Called from network socket logic with the network locked
 *
 ****************************************************************************/

int tcp_backlogdestroy(FAR struct tcp_conn_s *conn)
{
  FAR struct tcp_backlog_s     *blg;
  FAR struct tcp_blcontainer_s *blc;
  FAR struct tcp_conn_s        *blconn;

  ninfo("conn=%p\n", conn);

#ifdef CONFIG_DEBUG_FEATURES
  if (!conn)
    {
      return -EINVAL;
    }
#endif

  /* Make sure that the connection has a backlog to be destroyed */

  if (conn->backlog)
    {
      /* Remove the backlog structure reference from the connection */

      blg           = conn->backlog;
      conn->backlog = NULL;

      /* Handle any pending connections in the backlog */

      while ((blc = (FAR struct tcp_blcontainer_s *)
                    sq_remfirst(&blg->bl_pending)) != NULL)
        {
          blconn = blc->bc_conn;
          if (blconn)
            {
              /* REVISIT -- such connections really need to be gracefully closed */

              blconn->blparent = NULL;
              blconn->backlog  = NULL;
              blconn->crefs    = 0;
              tcp_free(blconn);
            }
        }

      /* Then free the entire backlog structure */

      kmm_free(blg);
    }

  return OK;
}

/****************************************************************************
 * Name: tcp_backlogadd
 *
 * Description:
 *  Called tcp_listen when a new connection is made with a listener socket
 *  but when there is no accept() in place to receive the connection.  This
 *  function adds the new connection to the backlog.
 *
 * Assumptions:
 *   Called from network socket logic with the network locked
 *
 ****************************************************************************/

int tcp_backlogadd(FAR struct tcp_conn_s *conn, FAR struct tcp_conn_s *blconn)
{
  FAR struct tcp_backlog_s     *bls;
  FAR struct tcp_blcontainer_s *blc;
  int ret = -EINVAL;

  ninfo("conn=%p blconn=%p\n", conn, blconn);

#ifdef CONFIG_DEBUG_FEATURES
  if (!conn)
    {
      return -EINVAL;
    }
#endif

  bls = conn->backlog;
  if (bls && blconn)
    {
      /* Allocate a container for the connection from the free list */

      blc = (FAR struct tcp_blcontainer_s *)sq_remfirst(&bls->bl_free);
      if (!blc)
        {
          nerr("ERROR: Failed to allocate container\n");
          ret = -ENOMEM;
        }
      else
        {
          /* Save the connection reference in the container and put the
           * container at the end of the pending connection list (FIFO).
           */

          blc->bc_conn = blconn;
          sq_addlast(&blc->bc_node, &bls->bl_pending);
          ret = OK;
        }
    }

  return ret;
}

/****************************************************************************
 * Name: tcp_backlogremove
 *
 * Description:
 *  Called from poll().  Before waiting for a new connection, poll will
 *  call this API to see if there are pending connections in the backlog.
 *
 * Assumptions:
 *   Called from network socket logic with the network locked
 *
 ****************************************************************************/

bool tcp_backlogavailable(FAR struct tcp_conn_s *conn)
{
  return (conn && conn->backlog && !sq_empty(&conn->backlog->bl_pending));
}

/****************************************************************************
 * Name: tcp_backlogremove
 *
 * Description:
 *  Called from accept().  Before waiting for a new connection, accept will
 *  call this API to see if there are pending connections in the backlog.
 *
 * Assumptions:
 *   Called from network socket logic with the network locked
 *
 ****************************************************************************/

FAR struct tcp_conn_s *tcp_backlogremove(FAR struct tcp_conn_s *conn)
{
  FAR struct tcp_backlog_s     *bls;
  FAR struct tcp_blcontainer_s *blc;
  FAR struct tcp_conn_s        *blconn = NULL;

#ifdef CONFIG_DEBUG_FEATURES
  if (!conn)
    {
      return NULL;
    }
#endif

  bls = conn->backlog;
  if (bls)
    {
      /* Remove the a container at the head of the pending connection list
       * (FIFO)
       */

      blc = (FAR struct tcp_blcontainer_s *)sq_remfirst(&bls->bl_pending);
      if (blc)
        {
          /* Extract the connection reference from the container and put
           * container in the free list
           */

          blconn       = blc->bc_conn;
          blc->bc_conn = NULL;
          sq_addlast(&blc->bc_node, &bls->bl_free);
        }
    }

  ninfo("conn=%p, returning %p\n", conn, blconn);
  return blconn;
}

/****************************************************************************
 * Name: tcp_backlogdelete
 *
 * Description:
 *  Called from tcp_free() when a connection is freed that this also
 *  retained in the pending connection list of a listener.  We simply need
 *  to remove the defunct connection from the list.
 *
 * Assumptions:
 *   Called from network socket logic with the network locked
 *
 ****************************************************************************/

int tcp_backlogdelete(FAR struct tcp_conn_s *conn,
                      FAR struct tcp_conn_s *blconn)
{
  FAR struct tcp_backlog_s     *bls;
  FAR struct tcp_blcontainer_s *blc;
  FAR struct tcp_blcontainer_s *prev;

  ninfo("conn=%p blconn=%p\n", conn, blconn);

#ifdef CONFIG_DEBUG_FEATURES
  if (!conn)
    {
      return -EINVAL;
    }
#endif

  bls = conn->backlog;
  if (bls)
    {
      /* Find the container hold the connection */

      for (blc = (FAR struct tcp_blcontainer_s *)sq_peek(&bls->bl_pending),
           prev = NULL;
           blc;
           prev = blc, blc = (FAR struct tcp_blcontainer_s *)sq_next(&blc->bc_node))
        {
          if (blc->bc_conn == blconn)
            {
              if (prev)
                {
                  /* Remove the a container from the middle of the list of
                   * pending connections
                   */

                  sq_remafter(&prev->bc_node, &bls->bl_pending);
                }
              else
                {
                  /* Remove the a container from the head of the list of
                   * pending connections
                   */

                  sq_remfirst(&bls->bl_pending);
                }

              /* Put container in the free list */

              blc->bc_conn = NULL;
              sq_addlast(&blc->bc_node, &bls->bl_free);
              return OK;
            }
        }

      nerr("ERROR: Failed to find pending connection\n");
      return -EINVAL;
    }

  return OK;
}

#endif /* CONFIG_NET && CONFIG_NET_TCP && CONFIG_NET_TCPBACKLOG */
